Biomechanical Analysis of Pole Vault Event › 6b18 › 01e16988bc0365863a1dc2… · 8 1994 by Human Kinetics Publishers, lnc. Biomechanical Analysis of the Pole Vault Event Rosa

JOURNAL QF APPLIED BIOMECHANICS, -1994,10, 147-165 8 1994 by Human Kinetics Publishers, lnc.

Biomechanical Analysis of the Pole Vault Event

Rosa M. Angulo-Kinzler, Stephen B. Kinzler, Xavier Ba lius, Carles Turro, )osep M. Caubet,

Josep Escoda, and ). Antoni Prat

This study explains the general aspects of the biomechanics of the pole vault and presents a 3D analysis of the best official performances of the top 8 pole vaulters at the 1992 summer Olympic Games in Barcelona. Two time code synchronized S-VHS video cameras operating at 50 Hz were used. All vaulters showed a reduced last stride and a low CM during the penultimate foot support. Great horizontal velocity at takeoff, high grip, and well timed angular momentum serve as good indicators of a jumper's performance. An early positioning of the hips parallel to the bar can be very beneficial, as can a close placement of the CM to the bar at the time of pole release. Finally, an advantageous bar clearance technique used by the winning Unified Team vaulters is noted.

This report is part of the High Bar, High Jump, and Pole Vault report that the Biomechanics Subcommission of the IOC approved to be conducted during the 1992 summer Olympic Games in Barcelona. The purpose of this report is to explain the general aspects of biomechanics of the pole vault and to analyze the performances of the 8 best finalist pole vaulters.

The pole vault event has undergone a great transformation since the use of fiberglass poles began. It is interesting to note the continuous improvement in the performance of this event over the last 20 years. Unlike some other track- and-field events that have reached performance plateaus in the past few years, the pole vault event still has considerable potential for improvement (an average increase of approximately 3 cm per year).

Methods and Procedures The 8 best finalist pole vaulters of the Barcelona summer Olympic Games were analyzed. Their average weight was 75.9 kg (SD = 1.9 kg) and their average

R.M. Angulo-Kinzler, X. Balius. C. Turn, J.M. Caubet, J. Escoda, and J.A. Prat are with the Biomechanics Department, Centre B'Alt Rendiment, Barcelona, Spain. S.B. Kinzler is with the Computer Science Dept. at Indiana University. R.M. Angulo-Kinzler is also with the Kinesiology Dept., HPER 112, Indiana University, Bloomington, IN 47405; request reprints from her at this address.

148 Angulo-Kinzler, Kinzler, Balius, et a/.

Table 1 Jumps Analyzed and Athlete Characteristics

H W Bar Jump HP PL Boxstd Name Country (m) O<g) (m) attempt (m) (m) (m)

Tarassov Trandenkov Garcia-Chico Tarpenning Volz Peltonieri Collet Krasnov

Unified Team Unified Team Spain USA USA Finland France Israel

Note. H = height and W = weight of jumper; Bar = height of attempted jump; HP = peak height of center of mass; PL = pole length measured from center of top handgrip to planting box; Boxstd = horizontal distance calculated from videotape between planting box and standards.

height was 1.83 m (SD = 0.06 m). Their pole lengths, the horizontal distances between the planting box and the standards, and the heights of the attempted jumps are specified in Table 1.

Two fixed JVC-KY 17 Fite S-VHS video cameras were used for the data collection. The cameras were located at 55 and 70 m from the planting box and were high enough to film the inside of the planting box. Their optical axes were oblique to the right side of the athletes' run-up, describing an angle of 60' between them. The field of view of both cameras was approximately 9 m on the horizontal by 6 m on the vertical. The cameras were genlocked and time code synchronized with the use of two Alpermann-Velte-TC30 time code generators. The time code was inserted in the video image with the use of two Alpermann- Velte-TC30 reader-inserters to facilitate the posterior analysis. We calibrated the space using an object of known coordinates and a volume of 6 x 3 x 1 m.

We used the direct linear transformation technique with 11 parameters (DLT-11) to calculate three-dimensional position coordinates of 22 body landmarks. A quintic spline function was used for smoothing and differentiation. The average mean errors for the estimation of 3-D points were RMS x = 0.005 m, RMS y = 0.008 m, RMS z = 0.003 m, and RMS total = 0.010 m.

Data collection was done at 50 Hz, and 22 body landmarks were manually digitized in each frame for both cameras. The resolution of the digitizer was 1,024 H x 960 V. We calculated the location of the center of mass using the height and weight of the athlete and Dempster's cadaver data (Dempster, 1955), with the trunk and head separated according to Clauser's data (Clauser, McConville, & Young, 1969). The moments of inertia of the segments about the transverse axis were calculated with Whitsett's data (Whitsett, 1963).

Several parameters were calculated for each analyzed jump with special emphasis on nine events (see Figure 1). The TD1 event (the touchdown of the

Analysis of the Pole Vault

, t I - ' -

-

Run-up Take-off Pole support Free flight l D 2 l D 1 =TI0 MPB PR 7 ~ 2 PP PS HP

TO1

Figure 1 - Pole vault phases and events. TD2 = second to last touchdown; TO2 = second to last takeoff; TD1 = last touchdown; PP = pole plant; TO1 = last takeoff; MPB = maximum pole bend; PS = pole straight; PR = pole release; HP = peak height of CM.

takeoff phase) was defined to occur at time 10 s to facilitate comparison between athletes. Four different phases were defined and analyzed in each jump: run-up, takeoff, pole support, and free flight. Special note must be made of the limitations of this study. The athlete together with the pole was considered a unique system for the purpose of analysis. As a consequence, the interaction between the jumper and the pole could not be analyzed. Also, the run-up phase was limited to the last two strides except for one case (Tarpenning) in which the cameras' fields of view didn't allow us to analyze the touchdown of the penultimate foot support.

In general, TO is considered the first frame in which the athlete's foot appeared off the ground. TD is defined as the first frame in which the athlete's foot appeared to touch the ground, and PP is the first frame in which the pole was in contact with the box.

Biomechanics of the Pole Vault

For the purpose of analysis, we have divided the pole vault into four phases and have defined instants of interest (events) within each phase (see Figure 1):

150 Angulo-Kinzler, Kinzler, Balius, et al.

The run-up or approach phase, which includes the touchdown and takeoff of every foot support during the approach run. In our study, we will analyze only the last two foot supports. The events analyzed in this phase are penultimate touchdown (TD2), penultimate takeoff (T02), and ultimate touchdown (TL31). The takeoff phase, which includes TD1, pole plant (PP), and ultimate takeoff (T01). The pole support phase, which includes maximum pole bend (MPB), pole straight (PS), and pole release (PR).

* The free flight phase, which includes the PR and the peak height (HP) of the center of mass (CM).

Also, we will use the four-height division of the final jump height as defined by Hay (1985) (see Figure 2).

The ultimate goal of a pole vaulter is to obtain the highest possible peak height of CM, together with a rotation that will allow the athlete to clear the bar safely with all parts of the body.

Apart from a fast run-up, the vaulter also needs to get the body very much upside down at the time that the pole gives its main push. In this way, most of the pole force will be used to lift the pole vaulter's CM without producing excessive rotational effects. Some rotational force will be needed to go over the bar. In summary, the vaulter should acquire a position that will permit the pole

Figure Z - Height ranges. H1 = height of CM at takeoff (T01); H2 = difference between height of CM at TO1 and at pole release (PR); M3 = difference between height of CM at PR and at its peak (HP); M4 = difference between height of CM at MB and height of bar.


Figure 3 - Off-center pole force vector. F, = ground reaction force on the pole; T, = clockwise torque.

force to pass slightly off from the vaulter's CM, producing a large vertical push with the rotation needed for clearance of the bar (see Figure 3).

Run-Up Phase

The main objectives of the run-up phase are to obtain a large horizontal velocity or kinetic energy and to prepare for the planting of the pole. The pole vaulter needs a very fast run-up, but horizontal velocity cannot be as great as in "free running" for two reasons: the athlete (a) has to carry the pole and (b) has to be extremely accurate in positioning the takeoff foot.

A fast run-up is necessary but not sufficient for a successful jump. Compari- son of successful and faulty jumps for the same vaulter shows little difference in the individual approach profiles. Therefore, the cause of the problem is gener- ally not the run-up speed. On the other hand, the fastest run-up is useless if the positional requirements of the takeoff preparation are not fulfilled.

A longer penultimate stride and a shorter final stride are consistent characteristics of most vaulters. Reducing the length of the last stride enables the vaulter to raise the CM into the takeoff, which facilitates a smooth transition from the horizontal run-up velocity to the vertical takeoff velocity. In this way, the vaulter avoids excessive braking action and sudden changes in the CM's path.

A vaulter should aim for a maximally effective grip, trying to avoid an excessive forward-rotating moment of the pole during the pole plant phase. The limits of the grip height are compromised by the amount of kinetic energy developed by the vaulter. Greater approach speed will enable the athlete to use a higher grip, provided the athlete has the strength to control the resulting

152 Angulo-Kinzler, K;nzler, Balius, et a/.

increased reaction forces of the pole on the body and that any resulting increase in speed does not make the coordination of the jump too difficult.

Furthermore, the athlete must consider the effects of grip height during the takeoff phase. If the pole is grasped too far from the bottom end, the moment opposing the motion of the athlete-and-pole toward the vertical will increase in such a way that the athlete will be unable to bring the pole to the vertical position. On the other hand, if the pole is grasped too low, it tends to come to the desired final position before the athlete has time to effectively complete the sequence of movements designed to project his or her body upward into the air.

Takeoff Phase

It can be assumed that some kinetic energy will be dissipated during the takeoff phase. There are three reasons for this energy loss: the impact of the pole with the box, the backward thrust of the ground reaction force on the athlete's takeoff foot, and energy loss associated with the bending of the pole.

During the brief period of the takeoff, the athlete must generate sufficient vertical impulse while minimizing the loss in horizontal velocity and, at the same time, must bring the body into a good position for the energy transfer to the pole. Furthermore, the athlete must plant the pole just before or at TO1 (the instant at which the vertical takeoff velocity reaches its maximum).

The pole vaulter must have the takeoff foot directly beneath his or her top hand at pole plant. If the takeoff foot is placed behind the perpendicular line through the top hand, the vaulter may develop more momentum in the swing than can be controlled later in the vault. In addition, this distant takeoff may reduce the vertical force that the athlete can exert at takeoff, making it more difficult to bring the pole to the vertical position. If the foot is too far forward of the perpendicular line through the top hand, the vaulter experiences a sharp jerk at takeoff as he or she leaps forward against the restraint imposed by the right hand.

Fiberglass poles give greater heights in vaulting compared to the metal or bamboo poles used previously, because they permit the use of a higher grip and, by bending more, store more energy. Fiberglass poles provide an effective means of converting the vaulter's kinetic energy to potential energy. Also, a much wider hand spread can be used with fiberglass poles, allowing the direction of the pole bend to be more easily controlled. The distance between the vaulter's hands and the position of the arms permit him or her to exert longitudinal and perpendicular forces to initiate the bending of the pole (see Figure 4).

When the pole hits the box and stops, the forward inertia of the vaulter creates a bending force on the pole. At this point, the reaction force of the pole on the vaulter will slow down the vaulter's CM, as we mentioned before. Also, it will give the vaulter some small vertical velocity. But the most important effect of this reaction force is the generation of a counterclockwise (CCW) forward torque about the vaulter's CM, causing the vaulter to begin to rotate in that direction (see Figure 5).

At the same time, the lower hand exerts a force approximately perpendicular to the tangent of the pole at the hand's contact point. This force will facilitate the bending of the pole. It is evident that the use of a wide handgrip on the pole would permit an earlier and better controlled bending due to the use of


Figure 4 - Forces of the vaulter on the pole via the hands. Ft0, = longitudinal component of the hands' force; F,,, = perpendicular or lateral component of the hands' force.

Figure 5 - Generation of a forward torque. F, = ground reaction force on the pole; T, = counterclockwise torque.

perpendicular or lateral components of the force exerted on the pole by each hand in opposite directions. Also, this type of grip is useful in posterior phases: It further delays the forward or CCW swing of the CM in the early stages of the pole support phase, it helps speed up the CM when required later, and it assists in a more rapid straightening of the body during the pull-up and push phases.

However, there is one disadvantage of the action of the lower hand. The reaction force of the pole on this hand produces a backward or clockwise (CW) torque that tends to impair the up-forward rotation of the vaulter. In other words, it makes it more difficult to achieve the rock-back position.

In summary, the vaulter acquires the angular momentum required for the rotation of the pole about its base and for the rotation of his or her body about the CM from the kinetic energy buildup during the run-up and from the transfer action taking place during the takeoff phase.


At the end of the takeoff phase, the vaulter should move with a large horizontal velocity, with moderate vertical speed, and at a shallow angle of about 20" between the CM's resultant velocity and the horizontal plane.

Pole Support Phase

During the early stage of the pole support phase, the vaulter "hangs" from the pole for a short while in order to delay upward motion of the CM and CCW rotation. In this way, some local angular momentum is traded for an equal amount of remote angular momentum of the pole in the opposite direction. This exchange is essential at this particular instant. After this action, the vaulter has ensured the passing of the pole toward the vertical. The body now needs to move up and rotate in preparation for the bar clearance.

The pole and vaulter are rotating in opposite directions. The rotation of the vaulter will be maintained without too much difficulty until the vaulter's CM crosses the plane perpendicular to its trajectory and containing the vector of the ground reaction force acting on the pole. At this point, the torque reaches value zero and the torque changes sign1 (see Figure 6). From this point on, this reaction force will exert a CW torque on the pole vaulter's CM. This torque will gradually slow down the CCW angular momentum of the vaulter.

To help speed up the rotation of the body into the rock-back position, the vaulter can increase angular velocity by decreasing moment of inertia. In other words, the vaulter tucks in order to speed up forward CCW rotation. This tucking action also has another effect. As the legs (and therefore the CM) accelerate away from the base of the pole (i.e., away from the box), the hands, in reaction, tend to move closer to the box, thus increasing the force on the pole and causing the pole to bend more.

Before the CW torque acting on the vaulter decreases enough to bring the angular momentum of the vaulter to zero and change signs, the vaulter should be in the most upward and forward rotation with a half twist, ready for the pole release and the clearance of the bar.

When the pole initiates its extension, the vaulter has reached the most rock- backward position. Here the moment of inertia reaches its minimum. The pole will return most of the energy stored as elastic energy to the vaulter in the form of kinetic energy. This kinetic energy is in turn transformed into potential energy, which is equivalent to raising the vaulter's CM. As the pole returns the stored energy, the vaulter can add momentum and speed by pulling now and pushing later with the upper extremities against the pole.

In summary, after the vaulter reaches the maximum backward-rotated position, the body is extended again in an upward movement. This action makes the vaulter press harder on the pole, and in reaction the vaulter receives a vertical reaction force from the pole that helps achieve vertical velocity. Since the pole chord is rotating toward the vertical while these movements occur, it is important that the vaulter keep the CM close to or behind the pole. Failure to do so will result in a dropping of the body and, ultimately, a poor push angle. At the end

'We are assuming that the ground reaction force passes through the upper handgrip. In fact, it could pass through any point between the hands.


(Assuming that the ground reaction force passes through the upper hand)

Figure 6 - Torque generated by the pole on the vaulter during the pole support phase. F, = ground reaction force on the pole; T, = counterclockwise torque; T, = clockwise torque.


of this phase, the direction of the rotation of the vaulter's CM will, and must, reverse, since a certain amount of CW angular momentum is necessary for the clearance of the bar.

Free Flight Phase

The vaulter should gain some CW angular momentum in order to have a successful bar clearance. To obtain this, the vaulter must receive a slightly off-center reaction force from the pole, as mentioned earlier. This off-center reaction force will provide the most upward velocity possible with a small but sufficient CW rotation (see Figure 3).

The flight parabola of the CM is determined by the vertical and horizontal velocities, the height of the CM before pole release, and the angle of projection as the vaulter leaves the pole. The angular momentum of the vaulter and the horizontal velocity of the CM are constant after this point. Therefore, the correct complex combination of all the previous movements will place the body at the appropriate height and horizontal distance from the bar, in a favorable position over the bar, and with the right amount and direction of velocity and rotation. On the other hand, faulty previous movements may decrease the amplitude and/ or height of the CM's parabola due to a bad body position over the bar or an insufficient velocity or angular momentum.

Results

To illustrate the relative fastness of every jump (from TDl to HP), we created an accumulative bar graph (see Figure 7). This graph shows the partial time between two consecutive events, in addition to the total time, for each vaulter.

volz - Peltonieri m-1 Collet

Krasnov

Figure 7 - Time in seconds at which each event occurred relative to TD1 at 10.0 s.


Figure 8 - Tarassov: HP = 5.907 m, bar = 5.80 m.

Three graphs per vaulter were generated to summarize each vaulter's pararn- eters. (See Figures 8, 9, and 10 as examples for Tarassov.) Figure 8 illustrates a wire-frame figure sequence of the analyzed events. Figure 9 represents the horizontal and vertical velocities, Vh and Vz, respectively, of the vaulter's CM versus time. Figure 10 represents the moment of inertia, Ix, and the angular momentum, Hx, of the vaulter about the transverse axis through the CM versus time. Both parameters Ix and Hx were normalized by the height and weight of the jumper. Figures 9 and 10 have the event times indicated with vertical dashed lines with adjacent event abbreviations.

A single graph was generated to represent the pole parameters for each vaulter. (See Figure 11 as an example for Tarassov.) The graph includes the pole chord length (PC), the angle between the PC and the horizontal plane, and the angular velocity of the PC versus time. The event times have also been indicated with labeled vertical dashed lines.

Table 2 shows the values for the CM height of each vaulter at TD2, T02, TD1, and T01; also, the last stride length and the grip width are included. The average of the last stride length is 2.00 m (SD = 0.12). The average grip width is 0.58 m (SD = 0.04). The average CM height follows the expected path of a good vault. From 59.96% (SD = 1.23) of the jumper's height at TD2, CM height is maintained at the same level (M = 59.54%, SD = 1.05), then changes to 60.39% (SD = 1.08) at TD1, and finally it goes up to 69.20% (SD = 1.39) at T01.

The horizontal and vertical velocities for each vaulter are presented in Table 3. The resultant velocities at TO1 range from 7.89 m/s to 8.6 m/s (M = 8.17 m/s, SD = 0.22). The resultant velocities at PR range from 2.03 m/s to 2.98 m/s (M = 2.32 mls, SD = 0.32).

Table 4 presents the four-height division of the final jump height for each vaulter. We can appreciate differences within each height as large as 20 cm when we compare all jumps. Pole chord shortening at MPB, the maximal angular

158 Angulo-Kinzler, Kinzler, Balius, et a!.

10.00 1050 11.00 1150 1200 1250

Figure 9 - Velocities for Tarassov.

Table 2 Stride Length, Grip Width, and CM Heights (in meters)

Name


CMVTDl CMVTOl

Note. SLI = last stride length; GW = grip width; CMVTD2 = vertical distance between CM and tip of support foot at TD2; CMVTO2 = at T02; CMVTDI = at TD1; CMVTOl = at T01.

Analysis of the Pole Vault 159

Table 3 Horizontal and Vertical Velocities (in meterslsecond)

Name MVHl VHTDl VHTOl VHPR VVTOl VVMAX VVPR


Note. MVHl = mean horizontal velocity for last stride; VHTDl = horizontal vel. of CM at TD1; VHTO1 = at T01; VHPR = during free flight phase; VVTOl = vertical vel. of CM at T01; VVMAX = max. vertical vel. of CM; VVPR = vertical vel. of CM at PR.

APC (den, -...- 100.00 PC10 (m) ----------.

WPC (de%r) 90.00

------- e w t s

80.00

70.00

60.00

50.00

40.00

30.00

20.00

10.00

0.00

-10.00

-20.00

-30.00 10.00 1050 11.00 ll50

Figure 11 - Pole parameters for Tarassov.

Table 4 Four-Height Division of Final Jump Height (in meters)

Name HP H 1 H2 H3corr H4


Note. HP = peak height of CM; H1 = height of CM at T01, also called CMVTOI; H2 = difference between height of CM at TO1 and at PR; H3corr = diff. between height of CM at PR and at HP, corrected depending on VVPR, H4 = diff. between height of CM at HP and height of bar.


Table 5 Vaulters' Angular Momentum and Pole Parameters From MPB to HP

PCRED LMAX LHP APPR CMHHP TLMAX Name (m) (lo5 s-') ( I 3 s ) (0) (m) 6 )


Note. PCRED = pole chord reduction at MPB; LMAX = max. angular momentum of vaulter about tranverse axis through the CM, normalized by height and weight: IC = (1,000 . IC)/(W . HZ); LHP = angular momentum during free flight phase; CMHHP = horiz. distance between CM and bar at HP (neg. sign indicates CM is still on run-up side); APPR = angle of pole chord with horizontal at PR; TLMAX = time of LMAX.

Table 6 Lateral Positions of CM From TD1 to TO1 (in meters)

Name LATCMTD l LATCMPP LATCMTO 1


Note. LATCMTDl = lateral position of CM relative to midline of run-up at TD1; LATCMPP = at PP; LATCMTO 1 = at TO 1.

momentum, the angular momentum at PR, the angle between the pole chord with the horizontal at PR, and the horizontal distance between the vaulter's CM and the bar are shown in Table 5. Finally, lateral position of the CM relative to the midline of the run-up was calculated. Tables 6 and 7 show this lateral position for every event of the performance.

Discussion Most of the approach parameters analyzed in this study follow the established pattern of a good pole vault. In all the analyzed jumps, the last stride tends to


Table 7 Lateral Positions of CM From MPB to HP (in meters)

Name LATCMMPB LATCMPS LATCMPR LATCMHP


Note. LATCMMPB = lateral position of CM relative to midline of run-up at MPB; LATCMPS = at PS; LATCMPR = at PR, LATCMHP = at HP.

be relatively short. Also, the height of the CM does not increase during the takeoff of the penultimate foot support. All jumpers experienced an increase of about 10% in the CM's height at the time of the final takeoff when compared to the previous takeoff.

The mean horizontal velocity of the last stride in all analyzed jumps appears to serve as a good indicator of the jumper's potential performance, as does the horizontal velocity at the time of the initiation of the takeoff phase. However, we should expect exceptions to this pattern as the literature indicates. A fast run- up velocity is essential but not sufficient for a good pole vault performance.

Collet, especially, attains a high horizontal velocity (VH) during the run- up and takeoff phases, although his VH is moderate throughout the rest of the jump. In spite of this, he elevated his CM only to 5.73 m, compared to other jumpers who reached 5.77 m and higher with horizontal velocities lower than his.

Several factors may contribute to this result. The main factor is that he is the jumper with the lowest grip height, 4.83 m. This means that even under the most favorable conditions he could reach a maximum CM height of only 5.80- 5.90 m. This estimate is based on the maximum gain from grip height (PL) to peak height of the CM (HP) observed in Sergei Bubka (1.05 m). Except for this fact, Collet achieves the largest PL-HP difference (0.9 m).

With vertical velocity (VV), a similar phenomenon is observed. Jumpers with a larger VV at the end of the takeoff (VVTOl) tend to achieve better performances. Again, some exceptions can be found. Once more, Collet has a VVTOl similar to that of Tarassov, the winner. In spite of this, there is a difference in their HPs of approximately 17 cm. In addition to the differences in grip heights between these two jumpers, Collet has a smaller VH and VV at the time of pole release (PR) with a VHPR = 1.69 mls and a VVPR = 1.12 m/ s, compared to Tarassov's VHPR = 1.81 mls and VVPR = 1.62 mls. This fact implies a diminished potential for Collet to elevate his CM during the free flight phase (FF). In fact, Tarassov gained 19 cm during that phase while Collet gained


only 8 cm. This difference of 11 cm accounts for most of the final difference between these two jumpers.

One possible explanation for the reduced increase in the CM height during the FF phase for Collet is his bad body position at the end of the pole straight phase (PS). His hips are too low and distant from the pole. Therefore, his CM may also be too far from the pole. In this case, the push action of the vaulter on the pole would produce an excessive rotational torque with a poor vertical component. In fact, this is a very common mistake, observed in all the vaulters except for Tarassov. The other jumpers reach their maximum moment of inertia (Ix) closer to the time of PS rather than closer to PR. Only Tarassov increases his Ix very rapidly almost until PR, reaching his maximum closer to that instant of time. This allows him to keep his angular momentum constantly decreasing until just before the PR. At this point, his angular momentum increases, gaining the needed rotation for the bar clearance. Also, he maintains his hips close to the pole at PS, allowing him to have the most efficient free flight phase among all the analyzed jumps (he increases his CM height by 19 cm with a resultant velocity at FF of 2.43 mls).

Another factor that must be taken into consideration here is Tarassov's early preparation for the bar clearance. At the time of PR, his hips are already parallel to the bar, a state observed only in this jumper. We believe that this early preparation allows him to use the time between PS and PR to create vertical pole reaction forces by pushing down on the pole without concern for the twisting component of that reaction force.

Another variable that seems to be correlated with the performance of the jumpers is the maximum angular momentum of the vaulter during the jump (Lmax). The two jumpers with the lowest values of Lmax are the ones who elevate their CM the least amount above grip height (PL). These two jumpers are Peltonieri, with PL = 5.13 rn and HP = 5.74 m, and Krasnov, with PL = 5.16 m and HP = 5.66 m. The value of H3 (the difference in the height of the CM at PR and HP) shows that both jumpers are also in the lower end of the group, with H3 = 0.07 m for Peltonieri and H3 = 0.14 m for Krasnov. A possible explanation for the poor angular momentum and the small H3 of Peltonieri and Krasnov is that they were using grip heights that were too large.

Among the group with low H3 values, we find Trandenkov with H3 = 0.06 m and Collet with H3 = 0.08 m. A possible explanation for the small increase in CM height between PR and HP in Trandenkov is that he had a poor pole bend (1.37-m pole chord shortening, compared to the appropriate value of 1.50- 1.60 m). The poor pole bend together with his high angular momentum may have caused his bad position at the end of the PR. The pole was past the plane parallel to the standards that crosses the ground at the pole planting point. As a consequence, if the position of the jumper is considered, the reaction forces generated by the pole on the jumper had a small rotational component (LHP = 100 . s-I) and a poor vertical one (VVPR = 1.26 mls).

The reasons for the poor increase in Collet's CM height between PR and HP are of the same nature. As mentioned before, the main problem in Collet's free flight phase is his poor starting position at the time of PS and therefore the poor off-center force he generated.

Four jumpers seem to suffer the consequences of poor pole bend, 2 of them due to insufficient bending and 2 due to excessive bending. Tarpenning

and Trandenkov have the lowest increases in VV between TO1 and PS: 1.71 m/ s and 1.87 mfs, respectively. Also, these jumpers have the lowest values for the pole bend: 1.43 m (28.2%) for Tarpenning and 1.37 m (26.5%) for Trandenkov. On the other hand, the jumpers who show the greatest pole bends are Peltonieri and Krasnov, both among the poorest performers. This relationship brings us to the conclusion that a pole chord shortening between 1.50 and 1.60 m should be acquired, as previous literature has already suggested (Yagodin & Papanov, 1986).

It is worth mentioning that Trandenkov (second place) had the greatest CM peak height at PR. He was 10 cm higher than Tarassov (the winner) at that same time (5.82 m and 5.72 m, respectively). Except for the aforementioned problem with the poor pole bend, and therefore the poor vertical gain in the height of the CM, especially during the second half of the jump, Trandenkov would have been able to elevate his CM beyond 6.00 m. We are assuming that 20 cm is a good and reasonable CM height increase during the FF phase. It is interesting to note the low hip position of Trandenkov at the time of maximal pole bend as an indicative of "not enough time" to rock-back, or "not fast enough" rock-back action. We discard the second option since his angular momentum was the highest among all the analyzed jumps. In other words, we think that his insufficient pole bend made him move too fast in the run-up direction compared to the speed at which he performed his rock-back action.

Another parameter has been identified as a potentially good indicator of good technique and performance: the horizontal distance between the location of the CM at HP and the bar (CMHHP). The first 4 placed vaulters had CMHHP absolute values between 0 and 7 cm. On the other hand, the last 4 placed vaulters had CMHHP absolute values between 11 and 33 cm.

Volz and Krasnov show the worst adjustment problem for this variable (33 and 22 cm, respectively). We believe that Volz's adjustment problem comes from the large vertical velocity of his CM during the support phase (5.40 m/s) together with a large angular momentum and large angular velocity of the pole, especially during the first half of his jump. We believe that the angular velocity of the pole reached its peak too soon, and little or no rotation of the pole was left at the end of the jump. All these factors contributed to the early push-pull action of the vaulter in spite of the relative delay of the pole by the second half of the vault. In other words, Volz was ready to release the pole when the pole was still far away from the vertical position. This problem becomes obvious when we observe Volz's small horizontal velocity at FF and when we look at the wire-frame figure sequence in the individual results. A problem that is similar, but of a more moderate degree, can be observed in Krasnov's technique.

It appears that Garcia-Chico is the jumper who best compromised between his potential and his actual performance. However, he did have the worst VH during the FF phase among all jumpers. In spite of this fact, he was able to increase his CM height by 12 cm during the FF phase thanks to a relatively large VV at the time of PR. We believe that an increase in the angular velocity of the pole during the second part of the pole support phase, together with a delay in the change of the angular momentum to a clockwise rotation, would help him improve his VH at PR. To achieve this he would have to increase his pull-push action on the pole before and after the PS event.


Last, we want to highlight the knee flexor action observed in the Unified Team vaulters, Tarassov and Trandenkov. As soon as their knees passed the bar, they started a flexor action. This decreased their moment of inertia and, consequently, increased the angular velocity of the total body. We think that this technique might be beneficial since it improves the bar clearance due to the accelerated elevation of the trunk at this time.

References

Clanser, C.E., McConville, J.T., & Young, J.W. (1969). Weight, volume and center of mass segments of the human body (AMRL Tech. Rep.). Wright-Patterson Air Force Base, OH.

Dempster, W.T. (1955). Space requirements of the seated operator. (WADC Tech. Rep.). Wright-Patterson Air Force Base, OH.

Hay, J.G. (1985). The biomechanics of sport techniques (3rd ed.). Englewood Cliffs, NJ: Prentice Hall.

Whitsett, C.E. (1963). Some dynamic response characteristics of weightless man. (ARML Tech. Rep.). Wright-Patterson Air Force Base, OH.

Yagodin, V., & Papanov, V. (1986). Sergei Bubka-6.01. Legkaya Atletica (USSR), 11, 12-14.

Acknowledgments

We appreciate the assistance of Yilmaz Alp, Amalia Angulo, Peter G. Brueggemann, Phil Cheetham, Arcadi Coll, Jesus Dapena, Alberto Garcia-Fojeda, Young-Hoo Kwon, Mike Leigh, Jill Martin, Tom Moore, Steve Risenhoover, and Andreu Roig in camera setup, space calibration, and data collection, as well as the assistance of Hans Ruf for his pole vault technique comments. Also, special gratitude is given to the Comite Organizador Olimpico de Barcelona '92 (COOB-Spain) for assistance in the cable installation; to Peak Performance Technologies, Inc. (USA), for providing extra equipment for digitization; and to the Sporthochschule (Germany) for providing the recording equipment.

We would also like to acknowledge the collaboration of the Centro de Estudios e Investigaciones Tecnologicas (CEITSpain) in the three-dimensional graphics animation generated during the Olympic Games of Barcelona as a part of this project.

Documents

Biomechanical Analysis of Pole Vault Event › 6b18 › 01e16988bc0365863a1dc2… · 8 1994 by Human Kinetics Publishers, lnc. Biomechanical Analysis of the Pole Vault Event Rosa